Features of the mineralogical composition of granulometric fractions of agrochernozem typical of permanent winter wheat

The fractions of granulometric elements isolated by evaporation from the arable horizon of a typical agrochernozem were studied using the X-ray diffractometric method. According to the results obtained, the various dust fractions and the silty fraction differ markedly from each other in their mineralogical composition. Quartz is noticeably predominant in the pulverized fractions of agrochernozem, the content of which consistently decreases from 74.4% in coarse dust to 62.5% in medium dust and to 40.1% in fine dust. In the silty fraction, the quartz content was only 7.1%. The amphibolite-actinolite content is very low and ranges from 0.5% in the silty fraction to 1.5% in the coarse-grained dust fraction. The amount of microcline from the group of potassium feldspar varies from 2.5% in the silty fraction to 14.8% in the medium dust fraction. These three main minerals are present in all studied fractions of granulometric elements. Albite from the plagioclase group is found only in pulverized fractions and is contained in the range of 9.2-14.6%. It is characteristic that feldspars are confined mainly to the medium-dust fraction, where their total amount is 29.4%. The coarse-grained pulverized fraction is characterized by the absence of clay minerals; in the medium pulverized fraction, the total amount of clay minerals was only 7.0%. Clay minerals are mainly localized in the siltstone fraction, where their total amount was 66.8%, and a complex group of minerals prevails among them, represented by smectite and a mixed-layer formation of illite-smectite type with a content of 52.4%. fine dust, in which the total amount of clay minerals was 36.5%, occupies a kind of transitional position between larger dust particles and the silty fraction. Keywords: AGROCHERNOZEM, X-RAY DIFFRACTION ANALYSIS, GRANULOMETRIC FRACTIONS, QUARTZ, MICROCLINE, ALBITE, SMECTITE, MULTILAYER ILLITE-SMECTITE